Elsevier

Journal of Electrocardiology

Volume 41, Issue 6, November–December 2008, Pages 553-556
Journal of Electrocardiology

Study of surface electrocardiogram spectrum before and after pulmonary vein ablation in patients with persistent atrial fibrillation

https://doi.org/10.1016/j.jelectrocard.2008.06.018Get rights and content

Abstract

Atrial fibrillation (AF) is the most common clinical cardiac arrhythmia and is usually treated with the electrical isolation of the pulmonary veins from the atria. However, it is estimated that about 30% of the patients undergoing this therapy will develop AF again. The purpose of this study was to test the dynamic changes of the spectra calculated in surface electrocardiograms (ECGs) before and after the ablation of the pulmonary veins. Surface ECGs of 14 patients with persistent AF undergoing this intervention were considered for this study. The QRS-T waves were subtracted from the ECGs using common spatial pattern, isolating the electrical activity of the atrium. The spectrum was then calculated and the main frequency peaks were identified. The smaller peaks with amplitude below 50% of the maximum were discarded. Eleven of the patients were followed up after the intervention for 1 to 6 months. Two of the patients developed AF again; the other 9 remained in sinus rhythm. For most of the patients, the spectrum showed more order after the intervention. However, the main frequency did not experience a significant decrease in average (5.1 Hz [±1.3] to 4.9 Hz [±1.0]). Interestingly, the increment or decrease of the main frequency did not correlate with the recurrence of AF or not.

Introduction

Atrial fibrillation (AF) is the most common clinical cardiac arrhythmia.1 It is estimated that 1% to 2% of the general population is affected by this arrhythmia.2 This arrhythmia is associated with a high risk of thromboembolic events, especially stroke (about 0.5%-12% per year).3 In most patients, atrial fibrillation is induced by a very rapid, abnormal electrical activity arising from the pulmonary veins.4 Therefore, electrical isolation of the pulmonary veins from the atria has developed as a successful procedure to cure AF, especially in patients with normal heart structure and short durations of the arrhythmia episodes. However, patients with enlarged atria and long-standing atrial fibrillation have significantly different electrical properties of the atria. This is characterized by an inhomogeneous distribution of the refractory period along the right and left atrium.5

Studies using sophisticated data analysis for electrocardiograms (ECGs) of patients with AF are focused on the calculation of the main frequency of AF and have connected it with the response to several pharmacotherapies.6 This frequency can be calculated from the surface ECG using digital signal processing (filtering, QRS-T subtraction, and frequency analysis). This parameter appears to be crucial in the clinical diagnosis of AF and its response to therapy. Atrial fibrillation with low fibrillatory main frequency is more likely to terminate spontaneously and responds better to pharmacotherapy, whereas high-frequency AF is more persistent and refractory to therapy.7 It has also been observed that this main frequency is correlated with the success of internal cardioversion.8, 9 A large study of 175 patients with persistent AF showed that low main frequency AF had more probability of maintain sinus rhythm. In the contrary, a higher AF main frequency resulted in more probable relapse of the arrhythmia.10 This frequency analysis technique therefore allows the noninvasive monitoring of antiarrhythmic drug effects on the fibrillatory rate.11

It has been studied that the frequency study of the AF ECG can be a valuable diagnosis tool in the clinical practice. It may be used for the monitoring of the effects of pharmacotherapy and the prediction of the arrhythmia recurrence. However, in addition to the main frequency, other parameters can also be extracted from the spectrum. The spectral concentration or the morphology of secondary harmonics within the frequency domain could present new information about the nature and the development of the AF.

To our knowledge, the correlation of the frequency analysis of atrial fibrillation ECGs with the success of pulmonary veins ablation techniques has not been studied until now. This was the motivation for the investigations described in this article. It describes the change in the spectrum before and after the application of pulmonary vein ablation therapy and explores how these parameters may detect which patients will have satisfactory outcome maintaining stable normal sinus rhythm.

Section snippets

Methods

Surface ECGs of 14 patients with persistent AF undergoing this intervention were recorded within the electrophysiology laboratory at the German Heart Center in Berlin. The patients were 5 women and 9 men with a mean age of 58 (SD, 11). Pulmonary vein isolation was performed with the use of a 3.5-mm irrigated-tip ablation catheter (Navistar, Biosense Webster, Inc, Diamond Bar, CA). A decapolar circular mapping catheter (Lasso, Biosense Webster, Inc) was placed at the ostial site of the pulmonary

Results

Eleven of the patients were followed up after the intervention for 1 to 6 months. Two of the patients developed AF again, whereas the other 9 remained in sinus rhythm.

From the 2 patients of whom ECGs of 30 minutes duration were analyzed, the values of the main frequency (maximum) were calculated. The spectrum of the signal shown in Fig. 2 can be seen in Fig. 3. In one of the patients, the median value of the maximum frequency was 7.0 Hz with a SD of 0.4. Interestingly, also considering the

Discussion and conclusions

From the results, it can be deducted that the different peaks observed in the atrial fibrillation spectrum are mainly due to time variations in frequency rather than concurrent fibrillatory frequencies that occur at the same time. This observation agrees with what was stated in the literature.14

A reduction in the number of peaks in 12 of 14 patients has been observed. On average, the number of peaks decreased from 2.2 in average down to 1.7. The main frequency did not give relevant results.

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